Noble gases often are used in powder metal sprays and plasmas as well as processes requiring chemically inert gaseous blankets and purges. When used in these processes they often become contaminated with trace levels of contaminants or impurities such as hydrogen, oxygen, and carbon monoxide. The presence of these contaminants and impurities in the noble gases, in the absence of treatment, generally prevents them from being reused in the processes.
Noble gases are quite expensive and thus systems have been developed to recover the gases from the various processes and to remove the trace contaminates and impurities therefrom prior to being recycled for reuse. Argon is the primary noble gas employed in inerting processes, and because a large volume of argon is used leading to a corresponding high cost for its use, systems have been developed to remove the impurities from argon streams.
Representative patents and articles relevant to the diverse ways for effecting recovery and purification of noble gases, and particularly argon, from process streams include:
U.S. Pat. No. 4,816,237 discloses the recovery of an argon stream from a silicon furnace and the subsequent purification of the argon gas having hydrogen as one of the many contaminants.
U.S. Pat. No. 4,983,194 discloses a process for the recovery of argon from an air separation unit.
U.S. Pat. No. 6,113,869 discloses a process for purifying an argon gas stream containing water, CO, CO2, hydrogen and other common impurities to such waste streams.
U.S. Pat. No. 6,123,909 discloses a process for purifying argon in a multi-step process using catalysts.
U.S. Pat. No. 6,531,105 discloses a process for treating a nitrogen stream recovered as a non-permeate from a membrane separation process.
US 2005/0025678 discloses a process for treating an argon stream as might be obtained from a high temperature furnace for producing silicon wafers.